The subject matter of the present disclosure relates to lighting and lighting devices and, more particularly, to embodiments of a lighting apparatus using light-emitting diodes (LEDs), wherein the embodiments exhibit an optical intensity distribution consistent with common incandescent lamps.
Incandescent lamps (e.g., integral incandescent lamps and halogen lamps) mate with a lamp socket via a threaded base connector (sometimes referred to as an “Edison base” in the context of an incandescent light bulb), a bayonet-type base connector (i.e., bayonet base in the case of an incandescent light bulb), or other standard base connector. These lamps are often in the form of a unitary package, which includes components to operate from standard electrical power (e.g., 110 V and/or 220 V AC and/or 12 VDC). In the case of incandescent and halogen lamps, these components are minimal, as the lamp comprises an incandescent filament that operates at high temperature and efficiently radiates excess heat into the ambient. Many incandescent lamps are omni-directional light sources. These types of lamps provide light of substantially uniform optical intensity distribution (or, “optical intensity”). Such lamps find diverse applications such as in desk lamps, table lamps, decorative lamps, chandeliers, ceiling fixtures, and other applications where a uniform distribution of light in all directions is desired.
Solid-state lighting technologies such as LEDs and LED-based devices often have performance that is superior to incandescent lamps. This performance can be quantified by its useful lifetime (e.g., its lumen maintenance and its reliability over time). For example, whereas the lifetime of incandescent lamps is typically in the range about 1000 to 5000 hours, lighting devices that use LED-based devices are capable of operation in excess of 25,000 hours, and perhaps as much as 100,000 hours or more.
Unfortunately, LED-based devices are highly directional by nature. Common LED devices are flat and emit light from only one side. Thus, although superior in performance, the optical intensity of many commercially-available LED lamps intended as incandescent replacements is not consistent with the optical intensity of incandescent lamps.
Yet another challenge with solid-state technology is the need to adequately dissipate heat. LED-based devices are highly temperature-sensitive in both performance and reliability as compared with incandescent or halogen filaments. These features are often addressed by placing a heat sink in contact with or in thermal contact with the LED device. However, the heat sink may block light that the LED device emits and hence further limits the ability to generate light of uniform optical intensity. Physical constraints such as regulatory limits that define maximum dimensions for all lamp components, including light sources, further limit that ability to properly dissipate heat.